1. Field of the Invention
The field of this invention relates generally to lighting fixtures, and more particularly to a parabolic louver and side light seal for use therein.
2. Description of Related Art
Overhead lighting systems have long been used to illuminate office, commercial, institutional, and industrial spaces. Such systems are commonly found in buildings that utilize xe2x80x9cdropped ceilingsxe2x80x9d which are hung from the floor platforms of the story located immediately above. Overhead lighting systems typically comprise a light fixture housing, or troffer. Troffers are conventionally designed in the shape of shallow, inverted, rectangular boxes having one open face. A series of light fixture housings or troffers are usually installed in a dropped ceiling, with each troffer carrying at least one tubular fluorescent lamp, HID lamp, or incandescent lamp therein, to serve as the light source.
Oftentimes, a transparent or translucent lens may be used to cover the open face of the light fixture housing. Such lenses are undesirable because they do not effectively prevent the escape of low angle light rays from the light fixture housings. These low angle light rays may create a glare that can be irritating to those individuals located in the space that the overhead lighting systems are designed to illuminate.
Accordingly, there have been several proposed solutions for eliminating or minimizing glare.
Coffers, for instance, are rectangular recesses formed in a ceiling at spaced intervals that are designed to house the light fixture housings. In order for a coffer to effectively reduce glare, it must have deeper dimensions than the light fixture housings that it will contain. This is because light fixture housings are usually installed in the upper surface or wall of the coffer, allowing the remaining side walls of the coffer to act as barriers to escaping low angle light rays. Though generally effective in reducing glare, coffers are often costly to install, and in certain instances, coffers may be impossible to install if the architectural design of the building prevents it.
One preferred method for reducing glare has been to direct the light radiating from a troffer downward using a louver. A louver is a grid-like structure comprising a series of blades (or baffles) arranged perpendicular to one another and interlocked to form a series of more or less equally sized square or rectangular openings. A louver is typically mounted directly beneath the lighting tubes of light fixture housings, or troffers, such that the bottom edge of the louver is more or less flush with the plane of the ceiling. A louver is typically assembled from a series of lateral and longitudinal metal blades. It has also been known to fabricate single-piece, plastic louvers using conventional injection molding techniques. Plastic louvers may be undesirable, however, because of deterioration that can result when lamps that generate substantial amounts of heat are used, such as HID or incandescent lamps. Whether metal or plastic, the blades of most louvers are designed with parabolic side wall surfaces. These surfaces are shaped to reflect the light emitted from the lamps downward, thus avoiding the escape of the low angle light rays which produce glare.
In addition to a louver and a light fixture housing, some overhead lighting systems also include a light trap or light seal device. A conventional light trap device typically includes a pair of side rails and a pair of end rails which, in combination, form a substantially rectangular light trap that is disposed between the light fixture housing and the edges of the louver. The light trap serves to prevent the escape or xe2x80x9cleakagexe2x80x9d of any light from around the peripheral edges of the louver.
Examples of prior art louvers are illustrated in U.S. Pat. Nos. 4,268,897 and 4,849,867.
In U.S. Pat. No. 4,268,897 to Schierwagen et al., a louver for a lighting fixture is disclosed having a plurality of longitudinally-extending light baffles which are aligned at right angles to a plurality of transversely-extending light baffles. In order to assemble the louver, camming projections on the top wall sections of the transverse baffles engage deflectable tongues formed on the side wall surfaces of the longitudinal baffles. Additionally, slots are cut-out in each side wall of the longitudinal baffles, and locking apertures are cut-out in the top wall sections of the longitudinal baffles in order to facilitate the xe2x80x9csnap-inxe2x80x9d engagement of the two baffles. Having a longitudinal baffle with slots in the side walls and apertures in the top walls may be disadvantageous, as a more elaborate and costly machining and assembly process may be necessary as compared to baffles that simply have openings in a side wall only.
U.S. Pat. No. 4,849,867 to Glass et al., also discloses a louver for a light fixture comprising a plurality of longitudinally extending blades interconnected with a plurality of transversely extending blades. The louver is assembled by sliding the transversely extending blades into corresponding notches in the longitudinally extending blades. As a result of being joined together in this manner, the ends of the longitudinally extending blades protrude outward along the periphery of the two sides of the louver, while the ends of the transversely extending blades protrude outward along the periphery of the two ends of the louver. This is best illustrated in FIGS. 1 and 2 of the ""867 Patent. Since the entire outer periphery of the louver contains the protruding ends of the transverse and longitudinal blades, it would be difficult to add a substantially rectangular light trap that can sit in abutment against the peripheral edges of the louver. A more elaborate light trap would have to be designed that could surround the periphery of the louver while simultaneously accounting for the protruding ends of the blades.
It is these deficiencies, among others, that the invention of the preferred embodiments has overcome.
In response to the difficulties encountered in the prior art, a parabolic louver and side light seal are disclosed for use in an overhead lighting system. The parabolic louver and side light seal are disposed within a light fixture housing, just below one or more tubular lamps. The parabolic louver focuses the light radiated from the tubular lamps in a downward direction, while the side light seal, disposed around the outer periphery of the parabolic louver, prevents light rays from escaping in the space between the light fixture housing and parabolic louver.
A series of ultra-thin, lightweight aluminum stringers and baffles arranged perpendicular to one another comprise the parabolic louver. The stringers extend in the longitudinal direction, while the baffles extend in the transverse direction. Novel side and center joints provide the means by which the longitudinal stringers and transverse baffles are interconnected in a quick, easy, and secure manner, to form the parabolic louver.
With the exception of two side stringers and two end baffles that define the respective sides and ends of the louver, the stringers and baffles each have a generally xe2x80x9cV-shapedxe2x80x9d cross-section, with parabolic side wall surfaces designed to reflect light. The two side stringers and end baffles that form the outer periphery of the parabolic louver are designed having a curved side wall that extends upward from a base portion and terminates in an upper edge. The base portion of the two side stringers contains a curved lip portion that defines a channel for receiving and securing two side rails of a side light seal.
Various side light seal rail designs, together with the design of the side stringers, allow the two side rails of the side light seal to be mounted to the outer periphery of the parabolic louver. Since the rails of the side light seal are preferably made from steel, mounting them to the periphery of the louver has the effect of reinforcing the parabolic louver.
One advantage of the invention is the ability to provide a durable, lightweight, parabolic louver comprised of ultra-thin stringers and baffles. The stringers and baffles are preferably formed from anodized aluminum, resulting in a finish that increases resistance to dents and scratches while virtually eliminating any visibility of fingerprints or construction dust. Another advantage of the invention is that the baffles and stringers are interconnected via novel xe2x80x9csnap-togetherxe2x80x9d side and center joints. These joints allow the parabolic louver to be assembled in a quick and convenient, yet secure manner. The ease with which the stringers and baffles are manufactured and assembled facilitates the creation of various-sized louvers. The number and size of the longitudinal stringers and transverse baffles that comprise the louver can simply be varied in order to vary the number of cells in a louver for appearance and performance considerations, as well as to accommodate light fixture housings of differing size.
Yet another advantage of the invention is the ability to mount the side rails of a side light seal on the side stringers of the louver. The side light seal not only prevents light rays from escaping in the space between the light fixture housing and parabolic louver, but it also has the effect of reinforcing the parabolic louver. The side light seal may also be incorporated with mechanisms which not only prevent the baffles and stringers from separating, but also position the baffles and stringers precisely with respect to the light source.
These and other objects, features and advantages of the invention will be apparent through the detailed description of the preferred embodiments and the drawings attached hereto. It is also to be understood that both the foregoing general description and the following detailed description are exemplary and explanatory and not restrictive of the scope of the invention.